Thanks for the correction, no clue on German geography apart from the main towns!
That was how it was written in the Loss Card.
Any chance your German contact could refer to the website linked in my Post #5 to verify if he is talking about the rear gunner being identified as Krewenchuk, or is it two separate references, the rear gunner in his turret and later seeing ID papers for Krewenchuk, thus not necessarily being the rear gunner, but another body?
F/Sgt Crompton was listed as being their rear gunner.
Always worth an "ask" of the RCAF Archives to see if they have further details on ND388 in Krewenchuks casualty or personnel files.